The goal of this project is to understand the underlying physiological mechanisms of different involuntary movement disorders. We have continued characterization of inhibitory spinal reflex circuits in patients with stiffman syndrome (SMS), with a focus on presumptive GABAergic pathways. A battery of reflexes were studied in an additional 8 SMS patients, all of whom had antibodies reactive against GABAergic neurons. As found in patients studied in previous years, inhibition of H-reflexes by tendon vibration seems to be the most consistent abnormality. These patients have also been enrolled in a treatment protocol, with serial performance of a selected battery of reflex studies at three points in their treatment. We continue to recruit patients with clinical symptoms suggestive of an acquired startle disease, looking for candidates with possible autoimmune attack on glycinergic pathways. Four patients underwent physiological studies to characterize abnormalities in spinal and brainstem reflex pathways. We have continued to characterize the myoclonus in Gaucher's disease type 3; somatosensory-evoked potential amplitude correlates with the stage of the disease. We are evaluating the nature of the positive and negative movements in patients with Sydenham's chorea. We are doing physiological tremor analysis, including spectral analysis of EMG and accelerometry, in persons in families with essential tremor and in persons with various neuropathies. These investigations should help with the diagnosis of tremor as well as elucidate the pathophysiology. We have begun more intensive studies of periodic movements in sleep seen in patients with restless legs syndrome.